a(1)=1, a(n) = 6*a(n-1) + n.

Terms

a(0) =1a(1) =8a(2) =51a(3) =310a(4) =1865a(5) =11196a(6) =67183a(7) =403106a(8) =2418645a(9) =14511880a(10) =87071291a(11) =522427758a(12) =3134566561a(13) =18807399380a(14) =112844396295a(15) =677066377786